Radio training system for aircraft pilots



De- 12, 1950 R. c. DEHMEL 2,533,361

RADIO TRAINING SYSTEM FOR AIRCRAFT PILOTS Filed June 22, 1946 2 Sheets-Sheet l 9 a COMPASS Am:

ATTRNEY Dec. 12, 1950 R. QVDEHMEL 2,533,361

- RADIO TRAINING SYSTEM FOR AIRCRAFT PILOTS Filed Jurle 2,2,y 194e 2 sheets-sheet 2 .VAUA'AVVAVAVAV F Y COMEASS Afr/3 0F ou BYQIIQQM Patented Bec. 12, 1950 UNITED STATES Pl" QFFICE RAMI@ 'ERAENING SYSTEM FR AIRCRAFT PLOTS 17- Claims.

This invention relates to radio training systems for-aircraft pilots andv navigators, and particularly to simulated radio range andr direction finding systems used in connection with grounded flight trainers;

A trainingv system for familiarizing the student pilot with methods of. obtaining quick and accurate radio compass; bearings. and. the usual radio range information should reproduce as faithfullyl as possible the commonly used and approved technique. For example, in a presently used system for obtaining during actual flight anauralnull indicationrofv the automatic radio compass `the pilot proceeds to shift theradio control switch to position loop and then to operate a motor reversing switchwhich controls rotation ofthe directional. loop. antenna. so as to bring in the null indication at his headphones. In this system theradiocontrol switchA can also be positioned so that the pilot may receive conventional radio range direction signals either cir-- clusively or in combination with a continuously indicating automatic radio compass.

lt is-- an object therefore of this invention to provide an: improved radio training. system of the above character that can be used inA present typegrounded` flight trainers for realistically simulating actua-l procedure for obtaining radio compass bearings and other radio direction data.

Another object oiv this invention is to provide g an improved electrical system including voltage resolvers controlled respectively inV accordance with-the. compassl'Iea-:ling` of theV trainer and the bearing@ of' the trainer position from a simulated radio station for automatically` obtaining the difference between the angles representing respectively they compass headingV of the trainer and the bearing of the radio station with respect to the trainer position, thereby determiningthe radio compass bearing of the trainer with respect to said radio station.

Another object of this invention is to provide an improved electrical system of the above character wherein the automatic radio compass can be made to adjust itself continuously to indicate the radio station bearing by means of a null positioning motor that is controlled by a voltage corresponding to a deviation of the compass reading from the true bearing.

Another and more specific object of this invention in o-ne form thereof is to provide an electrical resolving system for radio training systems of the above character that is simple and ei'lcient both in design and operation, and that eliminates duplicate circuits and equipment' by imposing on the same system a commercial power supply, suchk known- A and N radio range signals.

The invention will be morefully set forth in the followingv description-referring to the accompanying drawings,- and the features of novelty will loe pointed out with particularity in the claimsy annexedA to and forming apart of this specification;

Referring to the drawings,

Fig. 1- is a schematic layoutofl a radio training system for aircraft pilots` embodying the present invention,

Fig. Zfis a diagram illustrating the relationshipl ofz compass and radiol bearings` for agiven flight position, and

Eig. 3- isa circuit diagram illustrating an alternativearrangement for null signal control.

IngeneraLthe radio train-ing system comprises avoltage resolver I functioning as av transmitter and-arranged to be adjusted'tc: the angle-0 (trainer compass heading) ,.areceiving voltage resolver 2 arranged-,to be adjusted to the angle o; (direction bearing of a simulated radio station), a rotary transformer 3 connectedy tothe resolver 2 for simulating an automatic radio compass,l an operating motor il for the rotary transformer arranged to control'the radio'compass indicating element so as to indicate the diiierence Ibetween the angles@ and a thereby determining the radio compass bearing of the trainer with respect to the. simulated radio station as diagrammatically illustrated by Fig. 2, a rotary transformer 5 connectedto the transmitter l and functioning primarily as a. repeater for simulating a remote indicating compass to give the heading of the trainer with respect to a reference direction, usually northwa conventional radio range receiving system generally indicated at 8 :for aural indication of signals, such as the usual A and N signals, and control switching apparatus l for enabling the pilot to transfer from one radio direction system to another in accordance with established practice. For the purposes of this specification the term radio compass is intended to comprehend radio direction finders generally.

Referring now to the more specific details of Athe system, the transmitter l comprises a rotary single phase coil l@ connected to an operating shaft ll and a pair of iixed coils i2 and i3 arranged in quadrature with a common ground connection at lli. Therotatable coil or winding e, I is energized from a conventional 60 cycle alternating current supply source e through a suitable filter 8 and also from the output of a radio range signal simulating system including an oscillator source such as a 1G20 cycle supply commonly used for radio range signals through an amplifier 9a and slip-ring connection Ia. The other terminal of the coil is grounded through a slip-ring connection l 0b. A suitable lter for the signal circuit is provided by the condenser 9 and the inductance of coil l?! assuming that said inductance is suiiiciently high.

Accordingly there will be induced in the fixed two-phase windings l2 and i3 voltages from the cycle .supply and superimposed radio range signal voltages depending on the angular relationship of the single phase coil I0 to the iXed two-phase ouadrature windings. Assuming for example that the shaft El and therefore the coil l0 is rotated from a Xed reference position, such as the north compass position through an angle 0 and that the voltage in coil In is represented by E the voltage induced in coil I2 may be expressed as E sin fl and the voltage induced .in coil as E cos 0. These voltages are transmitted by means of the coil terminal conductors i5 and I6 to the common conductors I7 and I8 for supplyiner the two-phase fixed windings of both the rotary transformer 2 and compass repeater 5.

Referring rst to the rotary transformer 2, the two-phase fixed primary windings I9 and 2i] are arranged in. ouadrature in inductive relation to the rotatable two-phase ouadrature windings 2! and 22 which are connected to the rotatable shaft F3 .i or angular adjustment with respect to the fixed windings. The shaft 23 is positioned in accordance with the direction hearing relative to north of a simulated radio station on which a bearing is desired and it will be seen that when the shaft 22 is rotated from a sed reference position. .such as the aforesaid north reference position through an angle a corresponding to the instant flieht position bearing from the station, the voltage induced in the secondary winding 2i may be expressed in terms of the primary voltages as E sin 0 cos a-i-E cos 0 sin a and the induced voltage in winding 22 as E cos 0 cos a-i-E sin 0 sin a In other words, the Cartesian coordinate system to which the quadrature voltages E sin 0 and E cos 0 may be referred can be considered as rotated through the angle a hv means of the quadrature windings 2| and 22 of the two-phase to twophase resolver. Apparatus of this character is also disclosed in rnv copending application S. N. 560.288 filed October 25, 1944 for Coordinate Conversion and Vector Apparatus. This application has matured into Patent Number 2.510,- 384 dated June 6, 1950. The induced voltages in the quadrature windings 2i and 22 are transmitted respectively by means of slip-ring connections 2in. and .22a and terminal conductors 24 and 25 to the xed quadrature windings 20 and 21 of the rotary transformer 3 which simulates the automatic radio compass. The other terminals of the windings are grounded through the common slip-ring connection 2lb. f

It is suicient for the purposes of the present invention to refer generally to the operating means for the trainer compass bearing shaft Il and the ight position bearing shaft 23 since any suitable means for positioning the shafts can be 4 used. For example, a system that can be used for controlling the operation of these shafts is disclosed in my Patent No. 2,366,603 granted January 2, 1945 for Aircraft Training Apparatus wherein the shaft 6l operated from the steering motor SM, Figs. 1, 2 and 23, corresponds to the present trainer bearing shaft H, and the signal controller shaft 102, Fig. 8, of the aforesaid patent corresponds to the present radio station bearing shaft 23. When so controlled the shafts l l and 23 are automatically adjusted to the angles 0 and v. respectively as above defined.

If it is desired to use the invention in connection with polar coordinate charting apparatus, the system disclosed in my copending application S. N. 511,732 filed November 25, 1943 for Navigation Apparatus for Aircraft and Training Devices can also be used. This application has matured into Patent Number 2,475,314, dated July 5, 1949. In this system, the compass shaft 40, Fig. 1, corresponds to the present shaft Il and the chart shaft 104, Figs. l and 11, corresponds to the present shaft 23.

Referring to Fig. 2, the angle 0 represents the angle relative to north of the direction of simulated flight of the trainer T, i. e. the trainer compass heading, and the angle a represents the angle in azimuth relative to north of the radio station direction with respect to the instant flight position of the trainer. Upon inspection it is seen that Accordingly the actual bearing [i of the radio station relative to the nose of the trainer is the angle (1 0-H80", and it is the function of the radio compass to indicate the angle Automatic indication of the simulated radio compass or direction-finder 3 is obtained by means of the two-phase motor i that is connected through a speed reduction gear box 28 to the shaft 23 which carries a single phase coil 30 disposed in inductive relation to the quadrature windings 26 and 2 and a compass pointer element 2S cooperating with a suitable azimuth scale 29' for indicating the aforesaid radio station bearing. The pointer element 29 is preset 180 with respect to its zero reference position in order that the angle instead of the angle -180, may be directly read on the azimuth scale 29'. The reason for this 180 adjustment will he apparent from the fact that the angle a is taken from the radio station to the flight position whereas the angle is that taken from the aircraft, thus representing a shift of 180. One terminal of coil 30 is connected through a slipring connection Sd toa circuit conductor 32 and the other terminal is grounded through slip-ring connection 30D.

'fue motor is controlled in accordance with the voltage induced in the coil 30 so as to rotate the coil Si] in one direction or the other depending on the magnitude and sense of the induced voltage therein until a balanced or null position is reached where no voltage is induced in the coil. At this point the motor is de-energized and stops. :le corresponding position of the coil. 30 represents the angle a-o and the radio station bearing can be read directly from the compass element 2S and scale 29. Specifically, this is accomplished by energizing a phase winding 3i of the motor in accordance with the voltage of coil Sii through the slip-ring con ection 3de, conductor 32, contacts 33-30 of the switching apparatus '1, and the amplifier 35 which also is designed to function as a phase shifter.

massicci.

'I-he other pliase winding of stabilizing the operation of the motor 5' and: also toprovide for its operation! at? a'.y normally linear' speed characteristic with respect'.` tof the voltage' of coil te.; them'otoif mayy be: connected to a feed-back generator 3T3E having t`w0phase windings and. S92. winding` is ener"-` gized from the 60 cycle A. C.A supply' eandl the Voltage induced in winding 33,-wlii is proportional' to' the motor-generator' speed) andl has an instant polarity opposite to that or the signal. at Contact. Sens dzb'acliby conductores toftne'id put. of the amplifier' 35i for; inodiiyingf the inputVv current to winding 3l in awell'li-nown manner.

AccordinglyA it will be seen that asV the: phase relationship of the voltage in coil.' 3i; and hence that in motor winding'ti-Varies-withina. range of' lil()`c` the motor fi will operate in onefdire'ctiony or the'other andl at aspeed corresponding' to the magnitude of'- tlic Voltage which is' proportional to the extent ct. deviation of compass element Q9v from theI true bearing. This operation continues untilk the: coilillfisl rotated to a neutral or balanced position where no voltage isy induced' therein. Overshooting. or"l the null position' is therefore"precludedl since the motor speed isreAi ducedl in anticipation of the' null. Automatic' and continuous operation of the radiocompass can therefore be obtainedY by the pilot as long as the contacts @Q -154i closed on the com passi position; At the saine time, the radio range signal systemV is inl normal oper-ation: throughthe contacts fil-0:2" of thefswitc'ning ap paratus, the slidingv contacts and i2 being mechanically connected to each other as indicated at :'53 for simultaneous operation b-ythel pilot.

A suitable radio range signal system, such as that disclosed in my patentaboV-eA cited. may be used and further description thereof ils-unnecessary for a complete understanding of the present invention other thanl topoint out that-the.

the-leit'tothe ofi position so esto-engage. the fgrounded contacts eiland 5l.

In the radio` compass. system so far described the pilot relies on visual. indication solelyI for. checking his bearing. lt is: also desirable in practice to use the sc-called aural null method foran instant bearing. According to this methodvr thev directional loopantennarof the aircraitis rotated` either by a crank by the pilot, or by a motor until'. the plane or" theloop is-norinal to the directionoithe radio station. In this positionl practically no signal voltage is induced inthe loop and a null isindicatcd at the pilots headphones; It will be apparent that in this case there will be two nulle each 189 apart. The bearing of the radio station therefor-e can be determined from the angular position: ot the loop with respect tothe longitudinal axis of: the aircraft and; theobserved compass reading by' standard. orientation procedure;

According tothe-*present inventionst-his method 3e: isfeI-Iergized-A from? the^ usual 60? cycle A.` supply e.: For' the purpose,`

6u is simulated by'me'ansof a contrrol` systemforcon ncctingrtne coil 3a to the pilots headphone system and operating the motor i in one direction or' tlieother'by means-ofl alreversing switch until thissystem; the-pilot'lrnovesf the. slider i3 to thev loop position' s'o that slider conta-cts ian'd 3A engage the: xedf contacts e and 53. which' are. connected respe'ctivelyby conductors' 541 and" 5'5" to.y the coil 38.- and the reversing switch RS.. This switch: comprises' a plurality' ofIV alined' contacts 5l?, 571:, 585- 591' and 60' eachmounted" on4v a1 leai spring and normallyspaced-l from each other asi illustrated; Thev terminal'sof contacts 55' and tu areconnected?respectively to 60v cycle A, C. supply sources e andi -l-e, referring to'instant polarities of'saidlsupply sources; Theterminal` ofthe centralv contact- 58' is` connected t'o the motor supply conductor' 55. These contacts' are operated by means of awalkingbea1n` type lever Sl having ove'rhanging. extensionsalined with the' contacts. The beam is p'ivotecl above" and centrally with respect to contacts' at eil. By' tilting-1 the switch handle 63'? totth'e right for example, con` tac'ts 5U, Eigzahd te' are engaged in sequence' so'a's to complete the circuit between thek source -l-e" andthe motor winding 3i to causerotation ofthe coil 3G in a given direction. lfiovenientof the switch handle toward" the left opens the closed contacts and' causes engagementoicontacts 55; 5l' and 58 so as'to connect the motor directlyfto the source -e, therebycausing rotation of." the coil 'l' inthe opposite direction. Inf order'to operate the motor at' low sp'ee'das the null position is: approached so as tov obtainfa morelprecise' been ing and to avoid overshooting, the' contacts' 5I and 58? are'shunted by-a' resistance 53', and theI contacts 5t and 59 are shunted by a resistance` e5 which are'included' in the motoriwindingcircuit when the switch handle isl tilted slightly soV asto close but ther contacts SQL-GU; or the con`-y tacts as the case may be". Thek central` contact 58" is grounded as illustrated through a'- resistance 66;

In View of the fact that the 1020i cycle oscillat'or supply may if' desired be superimposed on the 66 cycle power supply in one formof theinvention, itl willr be apparent that when the coil Et" hasbeen rot-ated to aY null position the oscillator frequency voltage will: al'sobe zero so that the'p'il'ot gets a nullindicationat his headphones. The pilot by operating the switch' ES to its fully closed position can bring the radio compassl tou/'ardv the null position fairly rapidly and then by chanffing tothe low speed? position can obtain a quite accurate reading of the radio compass bearing. In view ofthe' fact that the motor li' is now directly connected to a 6l) cycleA. C; source, the pilot opens the switch immediately upon reachingy the'l nulli indication and gets' hisV bearing from the radio compass element 29'. It will beepparent that the radio'compassshaft ZB'may be operated by amanualfcr-ank ifdesired for get-- ting the aural null reading.

Where desired, a remote indicating compass can also be simulated by nieansof the repeater 5'V which is provided with two-phase' nxed' quadrature windings l@ and?! connected directlyt'o'the transmitter l so as to be energizedby the voltages E sin'. @and E' cos e" respectively. A` phase winding 'i2 energizediromfal'cycle Ai. C; source e' through a sliperingconriectionild is mounted on a rotatable'shaft iin'indu'ctive rel'ationltothe Xed windings 'itl ands 'H' so that it tends to be f positioned according: to thel position of: coil;y Ill 7 of the transmitter. The other terminal of coil 'I2 lis grounded through a slip-ring connection 12b.

For the purpose of introducing "north turning error and acceleration error, a disturbing coil 74 energized through slip-ring connections 'ida and 'Mb by a voltage Ent variable between zero and an amount sufcient to cause deflection of the coil through a material angle is likewise mounted on the shaft 'F3 so as t0 modify the position thereof according to simulated turning and acceleration error. A simulated compass system including a disturbing coil of this character and means for producing suitable north turning error potentials, such as Voltage Ent for the remote indicating compass is disclosed in my copending application S. N. 624,442 led October 25, 1945 for Flight Navigation Training Apparatus. This application has been matured into Patent Number 2,506,998 dated May 9, 1950. However, the turning error voltage Ent may be introduced in any suitable manner, such as by means controlled by the instructor according to indicated turning of the trainer, The shaft 13 is connected to a compass pointer 15 which cooperates with u a suitable azimuth scale 76 for giving a remote indication of the trainer compass heading subject to the aforesaid north turning error.

An alternative arrangement for controlling the aural null signal when the control switch is on loop is shown by Fig. 3. Instead of superimposing the radio range signal current on the power current as in Fig. l, the radio range signals are controlled in accordance with the potential across the coil 35 of the simulated radio compass so that a null signal is obtained when the coil is in a null position. To this end, the coil 39 is connected by conductor 8o to the grid 3l of an electronic amplifying tube or triode 82, the output of which is delivered to and rectified by the diode valve 83. A suitable lter arrangement comprising capacitances 34 and 85 and resistance 8B is connected across the rectifier' load resistance 8l and the D. C. output is impressed on the anode 88 of the triode 89. The control grid 9E] of this triode is connected by conductor 9! through an audio control resistance 91a to the output of the radio range signal system, which is energized from a 1020 cycle source as previously explained. The triode load resistance 92 is connected by conductor 93 to the switch contact 52 at the loop position. Assuming now that the coil 3Q is offcente` with respect to its null position so that a potential appears across its terminals, the grid 8l of the amplifying tube 82 is energized accordingly. The amplifier o-utput is rectified and smoothed by the diode S3 and filter circuit 84-86 respectively so that a positive D. C. potential is impressed on the plate 88 of the triode 89. Since the grid 9D is continuously energized from the A-N radio range signal system it will be apparent that a 1020 cycle current will flow in the triode load circuit including resistance 92 as long as sufficient plate potential is maintained. Therefore when the control switch 'l is on loop the pilots headphones are energized from the load circuit of triode 89 through the amplifier 41, contacts 42, 52 and conductor 93. When the coil 30 is at its null position no potential appears at the grid 8| and therefore no output current is delivered to the rectifier for maintaining a signal sustaining D. C. potential at the plate 88. Consequently a null signal is obtained at the pilots headphones. This system can be used independently of the characteristics of the transmitter I and therefore does not depend on the coil IG havinga suitable inductance for filter purposes.

It should be understood that this invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. In a radio training system for navigators, -means for simulating radio compass equipment comprising voltage resolving means having relatively movable coacting parts, one of which is adapted for adjustment to an angle representing a trainer compass heading, a second Voltage resolving means having additional relatively movable coacting parts, one of which is adapted for adjustment to an angle representing a radio station direction bearing from a reference direction, both said resolving means being electrically interconnected with one 0f said resolving cans functioning as a transmitter and the other as a receiver so that one of said adjustments modifies the other, a radio compass indicating element, and electrical means solely responsive to resolved voltages resulting from said modified adjustment for positioning said element so as to represent the difference between said angles thereby determining the corresponding radio compass bearing angle with respect to said station.

2. In a radio training system for navigators, means for simulating radio compass equipment comprising a rotary transformer functioning as a transmitter, a second rotary transformer connected in receiving relation thereto, one of said transformers adapted for adjustment to an angle representing a trainer compass heading and theI other adapted for adjustment to an angle representing a radio station direction bearing from a reference direction, a third rotary transformer the primary winding of which is energized by the output of said second transformer, and a compas-s indicating element movable according to relative r rotation of the windings of said third transformer, said compass element being arranged to indicate the corresponding radio compass bearing with respect to said station when the potential induced in the secondary winding of said third transformer represents a null condition.

3. In a radio training system for navigators, means for simulating radio co-mpass equipment comprising voltage resolving means adjustable to an angle representing av trainer compass heading, a second voltage resolving means adjustable to an angle representing a radio station direction bearing from a reference direction, one of said resolving means functioning as a transmitter and the other as a receiver so that the resolved output of said transmitter is modified by the adjustment of said receiver, a third voltage resolver energized by the modified output of said receiver, means for adjusting said third resolver to a null condition in respect to the output potential thereof and a radio compass indicating element controlled by the aforesaid adjusting means for indieating at the null position the corresponding radio compass bearing of said station.

4. In a radio training system for navigators, means for simulating radio compass equipment comprising voltage resolving means adjustable to an angle representing a trainer heading, a second voltage resolving means adjustable to an angle representing a radio station direction bearing from a reference direction, one of said resolving means Vfunctioning as atransmitter and the other as a-receiver so .that the resolved output-of said-transmitter is modied bythe adjustment of said receiver, .a third voltage resolver energized bythe modified output of -said receiver, means for adjusting said third resolver to a null condition in respect .to the -output potential thereof, a source of signals .simulating radio range signals and a receiver therefor, .said source `being-related to said third resolver so that the adjustment to'said -null condition yalso causes null vreception of-said-signals, and a radio-compass indicating-element controlled by the aforesaid adjusting rmeans for indicating at the null position .the-corresponding radio compass bearing of said station.

15. In Va radio training system for navigators, means -for simulating radio -compass equipment -comprising voltage resolving means adjustable to an-a-ngle-representing a trainer compass heading, :a second voltage resolving-means.adiustable to an .angle representing a radio station directionbearing from a reference direction, one of said resolving means functioning as a `transmitter and the other-asa receiver-so that the resolved outlput of Vsaid transmitterds modied by the adjustment of said receiver, athird Voltage resolver energized-bythe inodiiied-output of said-receiver, motive means operatively connected to said-third voltage resolver-and responsive toits output po- :tential.for-adjustingsaid.third resolver-to a null Vcondition with respect 'to said output potential and afradio compass-indicating element controlled by the aforesaid adjusting means for indicating atlthe-nullposition the corresponding radio compass'bearing of said station.

6. In a radio training system for -navigators, ymeans for simulating radio compass equipment comprising -voltage resolving means adapted for -adjustments to angles representing a-trainercompass heading-anda radiostation direction -bearing from-a reference direction respectively, said -resolving means being arranged so that one-of said adjustments .modifies the other, a rotary transformerhaving-primary and secondary windings-theprimar-y Winding being energized by the modifi-ed output 4of said resolving means, said windingsbeng relatively-movable for obtaining a `null condition with respect to the secondary wind- `ing potential, amotorenergized according to said secondary windingpotential for producing-relative movement of-said windings until said null condi- :tion is obtained-anda radio compass indicating zelement movable according-to relative movement :ofl-said-'Windings for automatically indicating the Vcorresponding-'radio compass bearing-of said stav tion when said null condition-is obtained.

.7. vIn ra radio .training system for navigators, .means .for simulating radio compass equipment comprising vvoltage resolving means adapted for ,adjustments to angles representing a trainer compass heading and a radio station direction bearling from a .reference direction -respectiveiysaid .resolving means being energized -by a flow frequency power potential and also by .an audio -ireduency potential and arranged so that one oi ,said :adjustments ,modiiies .the other, a rotary K transformer lhaving primary and secondary windings, the primary winding beingenergized by the modified output ,of said resolving means, said windings being relatively movable for obtaining `a null condition ,with respect to the secondary .windingpotentiaL anieleetric motor energized according to .the :seconda-ry .Winding .loweirequency potential for causing relative movement of said windings to said null positie-n; an audio signal receiver arranged to be associated With-said secondary windings so that a null audio frequency signal -is also :obtained -at Athe .null position of -said windings, and Ya radio compass indicating elementmovabie according to reiative movement of said windings -ior indicating .the correspond- -ing radio compass bearing of said .station .when said-null signai isobtained,

f8. fin radio training system for navigators, means -for rsimulating radio compass equipment comprising vvoitage .resolving means adapted for ustinents .angles representing a trainer com- 4pass heading an kradio .stationdlrection bearing from-a reeneedirection respectively, said Vresolving :means .being arranged se .that .one .of Isaid adjustments .modifies the other, a rotary transformer having primary and secondarywind.- .ingafthe primarywinding being energized-,bythe modified .output of saii resoiving means, .said --Windings being relatively movable .for obtaining a .null-condition witnrespect to the secondary winding potential,.asource oi signals simulatingradio lrange signals .and .a Vreceiver therefor, a two.- .phasernotorone phaseor which is energized ac,-

cording to said secondary Winding ,potential vfor producing relative rrmovement of ,said windings until said nuiiconditionis obtained anda .radio compass .indicatingfelement .movable according :tO --relative movement of .sa'd .windings for Jauto.- maticaily .indicating 4the vcorresponding radio compass .bearing ci .-said station .when said null fconditioneis obtained.

.19. :Ina iradio training system for navigatore,

means for -simulating radio compass equipment .comprising volta-ge vresolving means adapted for adjustments to rvangles representing a train-.er .compass neadngand va radio stationdirection bearing :from la reference .direction respectively, said.res-olvingmeanseing ,ngedso thatone ,ofsaidiadjustments modines the other, a voltage `resolving unitenergisedjcy .the modified output .fof Y.said .resolving means, electric motor ar- :ranged .to be energized according .to the ,output .-potentiaioip said unit `for automaticallyadjusting said =unit to a A'null .position .in vwhich said out- .put potential -is Ya .miniinum, ieed-' ick control V-rneans responsiveto'the speed or" said motor lor stabilizing the .operation .thereof with respect .to :said output potential, and `a rac'iiocompass indicating element actuated by said motor ,for indicating the corresponding radio comns bearingoisad station at said null position.

10. :In -a .radio ,trainingsystein for navigatore, means for simulating radio compass equipment Vcomprising voltage.resolvingmeans adapted for .adjustmentstoangles representing a trainer. compassheadingand a radio .station direction bear.- ling ironia referencedirection re ectiif'elj/said resolving :means .being arranged so .that one of said .adjustments modiiies theother, a .voltage Aresolving unit energized-by the modiedoutput of said --resolving -means, an electric motor-arranged to-be energized for adjusting said unit -to a null position inv/nich its output potential is a minimum, a source oi signals simulating radio range signals and a receiver there-for arranged to'be associated with said unit so that a null signal is obtained at said null position, circuit controlling means for operating said motor under direction of the navigator and for concurrently connecting said receiver for null signal reception, and a radio compassindicating element actuated ,fT-. by said ,motor for indicating the corresponding said adjustments modies the other, a voltage s resolving unit energized by the modied output of said resolving means, an electric motor arranged to be energized either automatically according to the output potential of said unit or under the direction of the navigator for adjusting said unit to a null position in which said output potential is a minimum so as to simulate loop antenna adjustment, a radio range signal system including a receiver adapted to be controlled in accordance with the magnitude of said output potential for obtaining a null signal at said null position when said motor is under control of the navigator', and a radio compass indicating element actuated by said motor for indicating the corresponding radio compass bearing of said station at said null position.

12. in a radio training system for navigators, radio compass simulating apparatus comprising means adjustable to a direction angle for deriving a pair of quadrature voltages represent- :we

ing respectively quadrature vector components, means ior resolving and rotating said quadrature components for reference to another set of quadrature axes including a rotary transformer having a two-phase quadrature Winding energized respectively by said voltages, a second two-phase quadrature winding arranged in inductive relation to said first-named quadrature winding, and means for moving one of said quadrature windings with respect to the other through an angle represented by another direction angie whereby the set of quadrature axes to which the induced voltages in the phases of the second quadrature winding are referred are represented as rotated through said last-named angle, one of said angles representing a trainer compass heading and the other representing a radio station direction bearing from a reference direction, a second rotary transformer having a two-phase quadrature Winding energized by the aforesaid induced voltages and a single phase secondary winding, means for adjusting said second rotary transformer so as to produce a null voltage condition in said secondary winding representing the diiierence between said angles, and a radio compass indicating element positioned by said transformer adjusting means so as to indicate a radio compass bearing at the null position thereof.

l3. In a radio training system for navigators, radio compass simulating apparatus comprising means adjustable to a direction angle for deriving a pair of quadrature voltages representing respectively quadrature vector components, means for resolving and rotating said quadrature components for reference to another set of quadrature axes including a rotary transformer having a two-phase quadrature winding energized respectively by said voltages, a second two-phase quadrature winding arranged in inductive relation to said first-named quadrature winding, and means for moving one of said quadrature windings with respect to the other through an angle represented by another direction angle whereby the set of quadrature axes to which the induced voltages in the phases of the second quadrature winding are referred are represented as rotated through said last-named angle, an inductive device energized by said induced voltages for determining the difference between said angles and an indicator connected to said device for simulating a radio compass.

14. In a radio training system for navigators, means for simulating compass equipment comprising an inductive transmitter having a single phase primary winding energized from an A. C. source and a two-phase quadrature secondary winding, said windings being relatively movable through an angle representing a trainer compass heading, an inductive repeater having a twoi phase quadrature primary winding energized by the secondary output of said transmitter and a two-phase quadrature secondary winding, one phase of said quadrature secondary being energized from an A. C. source and the other phase energized according to simulated compass error, said repeater primary and secondary winding being relatively movable, a compass indicating element movable according to said relative movement so as to simulate a remote indicating compass, and means operatively connected to said transmitter and adjustable according to a radio station bearing for simulating a radio compass.

l5. In a radio training system for navigators, means for simulating radio compass equipment including electrical means adjustable to a plurality of direction angles, null indicating means energized from said electrical means and adjustable to a null voltage condition to represent a radio compass reading on a radio station, and

means operatively connected to said null-indicating means for detecting said null condition in a radio range signal system including a source of audio frequency current comprising a therinionic valve having an anode energized when a positive voltage condition as contrasted with a null voltage condition obtains at said null indicating means and a control grid connected to the audio frequency signal source, and a signal receiver connected to the output circuit of said valve whereby audio signals are received when said anode is energized and a null signal is obtained during said null voltage condition.

16. In a radio training system for navigators, means for simulating radio compass equipment including electrical means adjustable to a plurality of direction angles, null indicating means energized from said electrical means and adjustable to a null voltage condition to represent a radio compass reading on a simulated station, and means for detecting said null condition in a radio range signal system including a source of audio frequency current comprising amplifying means energized when a positive voltage condition as contrasted with a null voltage condition obtains at said null indicating means, means for rectifying the output of said amplifying means, a thermionic valve having an anode energized by the rectified output voltage and a control grid energized from the audio frequency signal source, and a signal receiver connected to the output circuit of said valve whereby audio signals are received when said amplifying means is energized and a null signal is obtained during said null voltage condition.

17. In a radio training system for navigators, means for simulating radio compass equipment comprising voltage resolving means energized by a power current and adjustable in accordance with the trainer compass heading and the radio station direction bearing respectively, null indioating means having relatively movable primary REFERENCES CITED and secondarywindings inductively related, the primary winding being energized by output potential from said resolving means, and said null The following references are of record in the le of this patent:

indicating means being adjustable to a null volt- 5' UNITED STATES PATENTS age condition with respect to said secondary windv Number Name Date ing to representa corresponding radio compass 1 612 11.1 Hemett Dec 28 1926 reading on said-station, and means for detecting 2'164412 Koster Jui 4' 1939 said null condition in a radio range signal system 2321799 Cone 'nmey15' 1943 including a, source of audio frequency current 1o 2'332523 Norde Oct 261943 comprising a tnermionic valve operatively con- 2'343945 Weather's Mar' 14' 1944 nected to said gfsecondary winding and having an 2366603 Dehmel Jan 2' 1945 anode energized according to the winding voltage 2395477 Gumley Feb 26 1946 and a control grid energized from the audio fre- 2498981 Loveu "Se 1'24 1946 quency signal source. and a signal receiver con- 15 2416727 Adorjar; air 4 1947 nected to the output circuit of said valve whereby 2417229 Alexandeggx'l "Mar '11 1947 audio signals are received when said anode is 2428999 Homen Oct' 14 1947 energized and 'a null signal is obtained during 2448544 Muuer Set 7 1948 said null voltage condition. 224601305 Muuer F511 1949 RICHARD CARL DEHMEL. 2o 2,485,331 Stuhrman Oct. 18, 1949 

